In electronics, solders are usually 60% tin and 40% lead by weight in order to produce a near-eutectic mixture (lowest melting point — below 190 °C [374 °F]). These are commonly designated Sn60/Pb40. The eutectic ratio of 63/37 corresponds closely to a Sn3Pb intermetallic compound.
In plumbing, a higher proportion of lead was used. This had the advantage of making the alloy solidify more slowly, so that it could be wiped over the joint to ensure watertightness. Although lead water pipes were displaced by copper when it was realized that the lead was poisonous, lead solder was still used until the 1980s because it was thought that the amount of lead that could leach into water from the solder was negligible. But even tiny amounts of lead have been found to be detrimental to health, so the lead in plumbing solder was replaced by copper or antimony, with silver often added, and the proportion of tin was increased.